Omega-3s

EPA, DHA and ALA are not interchangeable

The single most useful thing to understand about this category is that "omega-3" covers three different compounds with very different usefulness.

• EPA and DHA — the long-chain forms found in oily fish and algae. These are the biologically active ones and what the research is about.
• ALA — the short-chain plant form in flaxseed, chia, walnuts and rapeseed oil. Your body converts it to EPA at a rate typically under 10%, and to DHA at under 1%.

Which means a product marketed as omega-3 that contains only flaxseed oil is not a substitute for fish or algae oil. This is the most common misunderstanding in the category, and it matters most for people on plant-based diets who believe they have it covered.

Note the tinned tuna row. It is widely assumed to be an omega-3 source and contains roughly a tenth of what mackerel does.

What the evidence supports

Reasonable to good:

• Triglyceride reduction. Well established and dose-dependent.
• Blood pressure. Small but consistent reductions.
• Cardiovascular outcomes. Debated in magnitude, but the overall picture supports oily fish intake.
• Inflammatory conditions. Modest benefits in rheumatoid arthritis and some inflammatory conditions at higher doses.
• Correcting a low intake. Most people who eat little fish have low omega-3 status, and supplementing corrects it.

Weak or mixed — and this is where the fitness marketing lives:

• Muscle protein synthesis and hypertrophy. Some short-term signalling studies look interesting; longer trials measuring actual muscle gain are inconsistent and mostly unimpressive in young trained people.
• Recovery and soreness. Mixed. Some reduction in perceived soreness, unclear effect on actual recovery — see delayed onset muscle soreness.
• Joint pain in healthy people. Weak.
• Fat loss. No meaningful effect.
• Cognition and mood in healthy people. Inconsistent, though more promising in older adults and those with low baseline intake.

Dosing and what to buy

• 1–2 g of combined EPA + DHA daily for general health if you eat little oily fish.
• Read the EPA/DHA content, not the fish oil weight. A "1,000 mg fish oil" capsule typically contains 180 mg EPA and 120 mg DHA — 300 mg total. Reaching 1 g means three to six capsules, which changes the cost calculation entirely.
• Concentrated products are better value per gram of active omega-3 despite a higher price per capsule.
• Triglyceride or re-esterified triglyceride forms absorb somewhat better than ethyl ester. Worth a small premium; not worth agonising over.
• Algae oil is the vegan option, and it is where fish get theirs from. It provides EPA and DHA directly, unlike flaxseed.
• Take with a meal containing fat. Improves absorption and reduces aftertaste.
• Store in the fridge. Omega-3s oxidise. If capsules smell strongly rancid, discard them — oxidised fish oil is worse than none.

Or just eat fish. Two portions of oily fish a week — mackerel, sardines, herring or salmon — covers requirements at lower cost than most supplements, with protein and vitamin D alongside. Tinned mackerel and sardines are among the cheapest nutrient-dense foods available.

Safety and interactions

• Up to about 3 g/day of EPA+DHA is generally considered safe for healthy adults.
• Blood thinning is the main interaction. If you take warfarin, other anticoagulants, or regular aspirin, talk to your doctor before supplementing.
• Tell a surgeon before an operation. High-dose omega-3 is usually stopped beforehand.
• Mercury and pollutants are a concern with large predatory fish (swordfish, shark, some tuna) rather than with small oily fish or with reputable supplements, which are purified.
• Cod liver oil is not the same thing. It contains omega-3 plus large amounts of vitamin A, which has a real upper limit. Do not use it as your omega-3 source at high doses.
• Fishy burps are reduced by taking capsules with food, freezing them, or using an enteric-coated product.

Omega-6 and the ratio question

You will encounter the claim that modern diets have a badly skewed omega-6 to omega-3 ratio and that reducing omega-6 is essential. Some nuance is warranted.

• The ratio has changed substantially over the past century, largely through vegetable oil consumption. That part is true.
• Whether the ratio itself matters, as opposed to absolute omega-3 intake, is contested. Trials reducing omega-6 have not produced the benefits the theory predicts.
• Omega-6 is not harmful. Linoleic acid intake is associated with lower, not higher, cardiovascular risk in most cohort data.
• The practical advice is the same either way: eat more oily fish or supplement EPA/DHA. Raising omega-3 is better supported than crusading against seed oils.

See dietary fat and hormones for the wider fat-intake picture.

Common questions

Will omega-3 help me build muscle?

The evidence is weak in young trained people. Take it for general health instead.

How much do I need?

1–2 g of combined EPA and DHA daily, or two portions of oily fish weekly.

Is flaxseed a substitute?

No. ALA converts to EPA at under 10% and to DHA at under 1%.

Is krill oil better?

Absorption may be slightly better per gram, but it contains far less EPA/DHA per capsule and costs considerably more. Poor value.

Do I still need it if I eat fish?

Two portions of oily fish a week and you probably do not.

What is the vegan option?

Algae oil, which supplies EPA and DHA directly.

Does it help with joint pain?

Modest evidence in inflammatory arthritis; weak in healthy people with training-related aches.

Should I worry about oxidation?

Yes, somewhat. Refrigerate, buy from reputable brands, and discard anything strongly rancid.

The practical version

• EPA and DHA are the active forms; ALA from flaxseed converts at under 10%.
• 1–2 g combined EPA+DHA daily, or two portions of oily fish a week.
• Read the EPA/DHA figure, not the fish oil weight — a 1,000 mg capsule often has 300 mg.
• Good evidence for cardiovascular and inflammatory health; weak for muscle and recovery.
• Algae oil is the vegan source; flaxseed is not a substitute.
• Refrigerate it, take it with food, and discard anything rancid.